(1) Field of the Invention
The present invention relates to a two-component type developer for use in the electrophotography and electrostatic printing, and a process for the preparation thereof. More particularly, the present invention relates to a two-component type developer capable of realizing an excellent reproducibility of a fine image and a high density of a solid image area simultaneously, and also to a process for the preparation thereof.
(2) Description of the Related Art
A two-component type developer comprising a magnetic carrier and a toner is widely used for commercial electrophotographic copying machines, and in developing a charged image, a magnetic brush of this developer is formed on a developing sleeve having magnetic poles arranged in the interior thereof, and this magnetic brush is brought into sliding contact with a photosensitive material having the charged image to form a toner image.
Recently, a carrier composed of spherical ferrite sintered particles or a carrier composed of such sintered particles coated with a resin is widely used, and the resistivity of the magnetic carrier is generally increased for improving the quality of a copied image. If the resistivity of the carrier is increased, the reproducibility of line images is improved, but the density of a solid image area is often reduced because the edge effect.
Changes of electric characteristics by increase of the resistivity of a carrier in the above-mentioned two-component type developer have not been sufficiently elucidated, and it is still difficult to obtain an image which is satisfactory in both of the high density of a solid image and the reduced deviation in a line image area.